The present invention relates to a random number generating device that generates a random number.
If an improper, non-approved battery is attached to electrically-powered equipment (such as an electric power tool, an electrically-driven machine, etc.) that operates by receiving a power supply from a battery, the equipment may be broken. Also, if an improper, non-approved battery is attached to a battery charger that charges a battery, the battery may abnormally generate heat.
In this type of equipment or battery charger, it is known that when a battery is attached thereto, whether or not the attached battery is a proper battery is determined (authenticated) by using a random number (see, for example, U.S. Pat. No. 7,941,865).
In U.S. Pat. No. 7,941,865, it has been proposed to generate, as a random number, noise bits (lower bits) of an A/D converted value obtained by an A/D converter, so as to perform authentication of a battery by using the random number.